1. Field of the Invention
The present invention relates to an endoscopic apparatus, and more particularly, to an improvement of image display control for an electronic type endoscope which has a memory for a function (called the digital scan converter (DSC) hereinafter) that is capable of arbitrarily controlling the writing of a data in the memory, and the reading of a data from, the memory.
2. Description of the Prior Art
A prior-art electronic endoscopic apparatus which has a solid state image pickup element incorporated on the tip of the scope has in general a configuration as shown in FIG. 1.
In the figure, the electronic endoscopic apparatus includes a scope which has a solid state image pickup element 1a incorporated on its tip, a processing circuit 2 which converts a signal obtained by the solid state image pickup element 1a to a video signal of the NTSC or RGB systems, a DSC 3 which converts an output of the processing circuit 2 to a digital signal, stores it in a memory circuit, reads it out in a form desired, and outputs it by converting it back to an analog signal, and a television monitor 4 which displays an output from DSC 3 as an image. Light radiated from a light source 5 is led to the tip of the scope by means of a light guide, and is used to illuminate the interior of the digestive system or the like. Generally, DSC 3 allows the writing and reading out of data in an arbitrary form. Therefore, it is possible to carry out the inversion between left and right, the shift of the position, and the inversion between up and down of an image that is displayed on the television monitor 4.
On the other hand, there are various type of scopes such as forward-looking, sideward-looking, and oblique-looking, and moreover, their thickness varies depending upon the region to be inspected or the purpose of the use. Such structural differences lead to the various differences in the restrictions, and affect deeply the disposition of the solid state image pickup element or bring about the necessity of inserting a reflecting body such as mirror and prism in the light path. As a result, the focusing position on the solid state image pickup element differs for different type of scope, or the image may appear left and right reversed.
Furthermore, in the forward-looking type of scope, the solid state image pickup member is disposed in a longitudinal direction of the scope, therefore, it is necessary to insert the reflecting body.
For this reason, deviation in the image display position on the television monitor 4 due to the difference in various kinds of scopes, the left-right inversion, and so forth are corrected manually within DSC 3 to display a correct image at a predetermined position without left-right inversion.
The manual operation of the DSC 3 for the conventional system is complicated as well as annoying.
In addition, endoscopic apparatus used in medical diagnosis for obtaining an image by incorporating a solid state image pickup element in the endoscope has superior resolving power of image and function as an apparatus compared with the type that employs optical fibers. On the other hand, however, the configuration of the apparatus is intricate so there is a possibility of an interruption during inspection of the collection of images of the object to be inspected due to failures in the electrical circuit.
The image obtained by the solid state image pickup elements are converted in the processing circuit to the so-called composite bit signal (namely, a signal obtained by mixing a synchronizing signal and a video signal) or to the R, G, and B signal which is stored in a memory unit and also is sent to the television monitor to be used for image display.
This process is analogous to taking an image of a scenery or persons with a conventional television camera, and displaying it on the television screen. Just like in this case the image may fail to appear on the television screen due to failure in the television camera, in the case of an apparatus which utilizes solid state image pickup elements, there may occur a case in which the image on the television monitor is disturbed or display is interrupted due to failure, for instance, in the memory unit.
Such disturbances in the image or an interruption in display due to failure in the processing circuit or the like, has to be avoided by all means since it may result in a medical disaster, as mentioned earlier.
One method of preventing such a medical disaster before it happens may be to carry out strict checkup at the time of starting the apparatus and before starting the inspection. However, it is not easy in practice to discover a defective part in such a checkup.